1. Field of the Invention
The invention relates to the diagnosis and treatment of pain.
2. Description of the Related Art
Certain patients are distinguished by having pain whose presence is dependent on sympathetic innervation of the painful area. The pain may result from skeletal, soft tissue, or nerve injury. Terms such as reflex sympathetic dystrophy, Sudek's atrophy, and causalgia have all been used to refer to such patients. However, because the link between pain and sympathetic function is often vague or not specified in much of the literature concerning these nosological designations, the term "sympathetically maintained pain" (SMP) is used to refer to that aspect of pain which is dependent on sympathetic efferent activity in the painful portion of the body.
One method of diagnosis of SMP is by assessment of the results of a local anesthetic blockade of the sympathetic ganglia (LABSG) that innervate the painful part. Intravenous regional blockage (IVRB) of sympathetic function with guanethidine has also been advocated as a means to diagnose SMP. Sympathetic blocks may not only provide a basis for diagnosis of SMP, but, may in addition, prove to be therapeutic. That is, the pain may be diminished after one or a series of block may.
Several disadvantages apply to the use of LABSG and IVRB. (1) LABSG is subject to false negative results if the local anesthetic fails to anesthetize adequately the sympathetic ganglia. (2) LABSG is subject to false positive results on two accounts: the anesthetic may reach the somatic afferents in the nearby nerve roots and produce pain relief because of concurrent somatic blockade, and certain afferents may in addition course with sympathetic efferents. (3) Certain patients tolerate poorly the application of the tourniquet required with IVRB. (4) LABSG involves strategic localization of the needle prior to injection, so fluoroscopy is often needed. (5) With IVRB the guanethidine may enter the systemic circulation and produce unfavorable side effects. (6) A series of complications have been reported with LABSG, which include pneumothorax, injury to the kidney, inadvertent systemic application, spinal anesthesia, hemorrhage, etc. (7) It is difficult to evaluate placebo responses with both LABSG and IVRB.
A method of diagnosis and treatment that eliminates the recited difficulties of current procedures used for patients with SMP is not found in the prior art.
Therapeutic uses of the .alpha.-adrenergic compounds, for example, phentolamine and clonidine, are known in the art.
U.S. Pat. No. 4,801,157, issued Jan. 1, 1989, discloses the use of phentolamine as a vasodilator to treat impotence.
U.S. Pat. No. 4,310,535, issued Jan. 12, 1982, discloses the systemic use of phentolamine in combination with other drugs for use in the control of immune reactions.
The systemic administration of phentolamine and clonidine for controlling hypertension is disclosed in U.S. Pat. No. 4,250,191.
.alpha.-Adrenergic drugs have been found to be useful in the stabilization of intraocular lenses, as disclosed in U.S. Pat. No. 4,443,441.
U.S. Pat. No. 4,201,211, issued May 6, 1980, discloses the use of a clonidine patch for therapeutic use as a stimulant for the central nervous system.
Other uses have also been reported for .alpha.-adrenergic antagonists and agonists. However, the prior art does not disclose the painful site use of .alpha.-adrenergic compounds such as phentolamine and clonidine for the diagnosis and treatment of sympathetically maintained pain.